Optical angle sensor using polarization techniques
AssigneeThe Boeing Company
InventorsNicholas Albion, Romeal F. Asmar, Raymond W. Huggins, Glen E. Miller, Charles R. Porter
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Abstract
A three-phase angular position sensor is described in which three beams of light having polarization directions rotated 60.degree. to each other are passed through a polarizer, the rotational position of the polarizer representing an angle to be measured. The intensities of the beams transmitted through the polarizer uniquely encode its angle over a 180.degree. range. This range may be doubled, for example, by including a binary track. A two-phase angular position sensor is also described in which two beams have polarization directions oriented 45.degree. with respect to one another.
Claims20
An angle sensing system, comprising:
- (a) means for creating first, second, and third optical channel signals along first, second, and third optical paths, respectively, each channel signal comprising light in a wavelength range different from the wavelength ranges of the other channels;
- (b) modulation means for converting the first, second, and third optical channel signals into first, second, and third modulated signals, respectively, the modulation means comprising means forming first linear polarizers and second linear polarizers in each optical path, the first linear polarizers having transmission axes that are fixed with respect to a first reference direction, the second linear polarizers having transmission axes that are fixed with respect to a second reference direction, such that each optical path is characterized by an angular difference between the transmission axes of the first and second linear polarizers in the optical path, which angular difference is a function of an orientation of the first reference direction with respect to the second reference direction, the angular differences for the first, second, and third optical paths being different from one another;
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- (c) means for measuring intensities of the modulated signals, and for producing therefrom an estimate of an angular position of the second reference direction with respect to the first reference direction.
An angle-sensing system comprising:
- (a) means for creating first and second optical channel signals along corresponding first and second optical paths, respectively, each channel signal comprising light in a wavelength range different from the wavelength ranges of the other charmels;
- (b) modulation means for converting the first and second optical channel signals into first and second modulated signals, respectively, the modulation means comprising means forming first and second linear polarizers in each optical path, the first linear polarizers having transmission axes that are fixed with respect to a first reference direction, and the second linear polarizers having transmission axes that are fixed with respect to a second reference direction, such that each optical path is characterized by an angular difference between the transmission axes of the first and second linear polarizers in the optical path, which angular difference is a function of an orientation of the first reference direction with respect to the second reference direction, angular differences for the first and second optical paths differing from one another by about 45.degree.;
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- (c) means for measuring intensities of the modulated signals, to thereby produce an estimate of an angular position of the second reference direction with respect to the first reference direction.
Dependencies are inferred from the claim text.